Revealing mistake: When Ellie is traveling through space, she unbuckles herself from the chair to retrieve the compass. The chair then breaks off from the violent movements of the space pod, and slams up against the ceiling. At this moment, Ellie is in deep space in a completely weightless environment. She is floating, suspended in the pod and the chair itself floats a bit before being slammed upwards by the force of the pod movement. But, some small parts of the chair (bolts, etc.) are seen falling directly down, towards us in obvious full gravity; revealing that the scene was actually shot in normal gravity.

As Ellie runs up the stairs of the observatory after hearing the first audio transmission from space, she runs towards doors with two large glass windows in them. As she opens the doors, a crewman/cameraman is visible in the right window for a brief fraction of a second.